The present invention relates to an antireflection film having antiglare property, and a polarizer, a liquid crystal display device and an image display device using the same. The present invention also relates to a coating solution for forming the low refractive index layer of an antiglare and antireflection film.
An antiglare film, an antireflection film or an antiglare and antireflection film is generally disposed, in an image display device such as cathode ray tube display device (CRT), plasma display panel (PDP) and liquid crystal display device (LCD), on the outermost surface of a display where the reflectance is reduced by using the principle of optical interference so as to prevent reflection of external light which causes reduction in the contrast or reflection of an image.
An antiglare and antireflection film having an antireflection function is more excellent in such a performance than an antiglare film, and use thereof in a display is recently started.
However, if the antireflection function is imparted, the dust protection on the surface generally changes for the worse and dusts readily attach thereto. Dusts may be gathered on the display for removing the attached dusts but the gathered dusts cannot be removed from the display. This is a serious problem on considering using the antiglare and antireflection film for television in the future.
Heretofore, antireflection function and prevention of dusts from sticking cannot be attained at the same time.
On the other hand, in the antireflection film having only a hard coat layer and a low refractive index layer on a transparent support, the refractive index of the low refractive index layer must be satisfactorily lowered so as to reduce the reflectance. For example, in the case of an antireflection film having a triacetyl cellulose support and using UV cured film of dipentaerythritol hexaacrylate as the hard coat layer, the refractive index must be lowered to 1.40 or less so as to reduce the average reflectance to 1.6% or less in the range from 450 to 650 nm.
With respect to the material having a refractive index of 1.40 or less, the inorganic material include fluorine-containing compounds such as magnesium fluoride and calcium fluoride, and the organic material include fluorine compounds having a large fluorine content. However, these fluorine-containing compounds have no cohesion and therefore, are deficient in the scratch resistance as a film disposed on the outermost surface of a display. In order to have sufficiently high scratch resistance, a compound having a refractive index of 1.43 or more is necessary. As such, it is difficult to attain low refractive index and scratch resistance at the same time.
JP-A-7-287102 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) describes a technique of increasing the refractive index of hard coat layer and thereby reducing the reflectance. However, due to large difference in the refractive index between this high refractive index hard coat layer and the support, color irregularity is generated on the film and the dependency of the reflectance on the wavelength greatly fluctuates.
JP-A-7-333404 describes an antiglare and anti-reflection film excellent in the gas barrier property, antiglare property and antireflection property, where, however, a silicon oxide film by CVD method is indispensable and therefore, the productivity is low as compared with the wet-coating method of forming a film by coating a coating solution. Furthermore, the antiglare and antireflection film obtained as such is not satisfied in the antireflection property.
According to the knowledge newly found by the present inventors, for obtaining an antiglare and antireflection film excellent in the antireflection property, antifouling property, scratch resistance and clearness of transmitted image by all-wet coating, it is preferred to use resin particles having a narrow particle size distribution with a number average particle size by the Coulter method of about 2 to 3 xcexcm, in the antiglare hard coat layer. However, in view of the design of surface asperities, such an antiglare hard coat layer suffers from narrow latitude in the average particle size and the particle size distribution of the resin particles used and furthermore, grain-like planar failures are readily caused throughout the film due to a very small amount of coarse grains, environment and mixing of foreign matters mingled into the support or the like.
The present inventors have found that use of a transparent support having excellent smoothness is preferred for obtaining, by all-wet coating, an antiglare and antireflection film excellent in the antireflection property, antifouling property, scratch resistance and clearness of transmitted image and favored with high planar uniformity while reducing the planar unevenness at the wet coating and that in particular, a transparent support for use in the antiglare layer having excellent clearness of transmitted image is required to have high smoothness. The present invention has been accomplished based on these findings.
An object of the present invention is to provide an antiglare and antireflection film which can be formed by a wet-coating method and which is excellent in the antireflection property, antifouling property, scratch resistance, clearness of transmitted image and planar uniformity.
Another object of the present invention is to provide an antiglare and antireflection film which is favored with planar uniformity at the same time with various performances such as antireflection property, antifouling property, scratch resistance and clearness of transmitted image and which can be obtained by an all-wet coating method.
Still another object of the present invention is to provide an antiglare and antireflection film which can be simply and inexpensively produced only by forming an antiglare hard coat layer and a low refractive index layer on a support and which is favored with a sufficiently high antireflection performance, scratch resistance and antifouling property.
Still another object of the present invention is to provide a polarizer and a liquid crystal display device using such an excellent antiglare and antireflection film.
Still another object of the present invention is to provide a polarizer and a liquid crystal display device, which are satisfactorily prevented from the reflection of exterior light and at the same time, favored with excellent antifouling property and high scratch resistance.
Still another object of the present invention is to provide a liquid crystal display device excellent in the contrast, visibility and clearness of image, and favored with good planar uniformity.
Still another object of the present invention is to provide an antiglare and antireflection film excellent in the dust protection (prevention of dusts from sticking) and having a small reflectance.
Still another object of the present invention is to provide a polarizer and an image display device using an antiglare and antireflection film excellent in the above-described properties.
Still another object of the present invention is to provide a coating solution capable of forming a low refractive index layer, which is a layer constituting the antiglare and antireflection film, to have good coated surface state and a uniform coating thickness.
According to the present invention, an antiglare and antireflection film, a polarizer, a liquid crystal display device and a coating solution for a low refractive index layer having the following constructions are provided and the above-described object can be attained.
(1) An antiglare and antireflection film comprising a transparent support having thereon an antiglare hard coat layer and a low refractive index layer having a refractive index of 1.38 to 1.49, wherein the low refractive index layer is formed by a coating method, the solvent of the coating solution for forming the low refractive index layer comprises one or more solvent, and from 50 to 100% by mass of the solvent is a solvent having a boiling point of 100xc2x0 C. or less.
(2) The antiglare and antireflection film as described in (1), wherein from 90 to 100% by mass of the solvent of the coating solution is a solvent having a boiling point of 100xc2x0 C. or less.
(3) The antiglare and antireflection film as described in (1), wherein the solvent of the coating solution is a ketone and/or an ester.
(4) The antiglare and antireflection film as described in (3), wherein the solvent of the coating solution for the low refractive index layer is 2-butanone.
(5) The antiglare and antireflection film as described in (1), wherein the low refractive index layer comprises a fluorine-containing compound crosslinked by heat or ionizing radiation and has a kinetic coefficient of friction of 0.03 to 0.15 and a contact angle to water of 90 to 120xc2x0 C.
(6) The antiglare and antireflection film as described in (1), wherein the low refractive index layer contains inorganic fine particles having an average particle size of 0.001 to 0.2 xcexcm.
(7) The antiglare and antireflection film as described in (1), wherein the antiglare hard coat layer contains mat particles having an average particle size of 1.0 to 10.0 xcexcm and the portion other than the mat particles of the antiglare hard coat layer has a refractive index of 1.57 to 2.00.
(8) The antiglare and antireflection film as described in (7), wherein the mat particles contains a particle satisfying the following conditions (i) to (iii) with respect to the particle size distribution:
Conditions with Respect to Particle Size Distribution
(i) the number average particle size measured by the Coulter method is from 1.7 to 3.5 xcexcm,
(ii) the standard deviation of the particle size is 25% or less of the number average particle size, and
(iii) coarse particles having a particle size 3.0 xcexcm or more larger than the number average particle size or coarse particles 2.5 times or more larger than the number average particle size are contained in a proportion less than 5 particles/1xc3x97108 particles.
(9) The antiglare and antireflection film as described in (1), wherein a haze is 3.0 to 20.0% and the average reflectance of light with a wavelength of 450 to 650 nm is 1.8% or less.
(10) An antiglare and antireflection film having asperities on the surface, wherein the vertical release charge amount measured with triacetyl cellulose or polyethylene terephthalate at an ordinary temperature and an ordinary humidity is xe2x88x92200 to +200 pc (picocoulomb)/cm2 and the surface resistivity is 1xc3x971011 xcexa9/xe2x96xa1 or more.
(11) The antiglare and antireflection film as described in (10), wherein the vertical release charge amount is from xe2x88x92100 to +100 pc/cm2.
(12) The antiglare and antireflection film as described in (11), which is an antiglare and antireflection film in a post-saponification system of performing the saponification after coating the antireflection layer.
(13) The antiglare and antireflection film as described in (10), wherein the vertical release charge amount with triacetyl cellulose or polyethylene terephthalate under conditions of ordinary temperature and 10% RH is xe2x88x92100 to +100 pc/cm2 and the surface resistivity is 1xc3x971011 xcexa9/xe2x96xa1 or more.
(14) The antiglare and antireflection film as described in (10), wherein the low refractive index layer comprises a fluorine-containing compound crosslinked by heat or ionizing radiation and has a kinetic coefficient of friction of 0.03 to 0.15 and a contact angle to water of 90 to 120xc2x0 C.
(15) The antiglare and antireflection film as described in (1), wherein the transparent support is a triacetyl cellulose film obtained by dissolving triacetyl cellulose in a solvent and casting the prepared triacetyl cellulose dope using a single layer casting method or a multiple layer co-casting method.
(16) The antiglare and antireflection film as described in (15), wherein the triacetyl cellulose dope is a triacetyl cellulose dope prepared by dissolving triacetyl cellulose in a solvent containing substantially no dichloromethane, using a low-temperature or high-temperature dissolving method.
(17) A polarizer using an antiglare and antireflection film for at least one sheet of two protective films of the polarizing layer, the antiglare and antireflection film comprising a transparent support having thereon an antiglare hard coat layer and a low refractive index layer having a refractive index of 1.38 to 1.49, wherein the low refractive index layer is formed by a coating method, the solvent of the coating solution for forming the low refractive index layer comprises one or more solvent, and from 50 to 100% by mass of the solvent is a solvent having a boiling point of 100xc2x0 C. or less.
(18) A liquid crystal display device using, for the outermost layer of the display, an antiglare and antireflection film comprising a transparent support having thereon an antiglare hard coat layer and a low refractive index layer having a refractive index of 1.38 to 1.49, the low refractive index layer being formed by a coating method, the solvent of the coating solution for forming the low refractive index layer comprising one or more solvent, and from 50 to 100% by mass of the solvent being a solvent having a boiling point of 100xc2x0 C. or less.
(19) A process for producing an antiglare and antireflection film comprising a transparent support having thereon an antiglare hard coat layer and a low refractive index layer having a refractive index of 1.38 to 1.49, wherein the low refractive index layer is formed by a coating method, the solvent of the coating solution for forming the low refractive index layer comprises one or more solvent, and from 50 to 100% by mass of the solvent is a solvent having a boiling point of 100xc2x0 C. or less.